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Posted to notifications@couchdb.apache.org by GitBox <gi...@apache.org> on 2021/04/14 09:41:46 UTC
[GitHub] [couchdb] janl opened a new pull request #3507: log file truncation
janl opened a new pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507
Helps find corrupted files on servers with lots of shards.
test script:
```sh
#!/bin/sh
COUCH=http://a:a@127.0.0.1:15984
DB=x-test-goop
CURL="curl -s"
# file does not exist
ls ~/Work/asf/couchdb/dev/lib/node1/data/shards/00000000-ffffffff/$DB*.couch
# reset db
$CURL -X DELETE $COUCH/$DB
$CURL -X PUT $COUCH/$DB?q=1
# add docs so we have something to truncate
$CURL -X PUT $COUCH/$DB/doc1 -d '{"foo":"baaaaaah1"}'
$CURL -X PUT $COUCH/$DB/doc2 -d '{"foo":"baaaaaah2"}'
$CURL -X PUT $COUCH/$DB/doc3 -d '{"foo":"baaaaaah3"}'
# show that we can read from the db
$CURL $COUCH/$DB/_changes?include_docs=true
# truncate
FILE_NAME=`ls ~/Work/asf/couchdb/dev/lib/node1/data/shards/00000000-ffffffff/$DB*.couch`
FILE_SIZE=`ls -l $FILE_NAME | awk '{print $5}'`
NEW_FILE_SIZE=`echo "$FILE_SIZE-5000" | bc`
truncate -s $NEW_FILE_SIZE $FILE_NAME
# rm $FILE_NAME
REAL_NEW_FILE_SIZE=`ls -l $FILE_NAME | awk '{print $5}'`
echo "$FILE_NAME"
echo "fs: $FILE_SIZE, nfs: $NEW_FILE_SIZE, rnfs: $REAL_NEW_FILE_SIZE"
# show error
$CURL $COUCH/$DB/_changes?include_docs=true
```
Response without the patch:
```erlang
{"error":"error","reason":"{{{badmatch,eof},\n [{couch_file,read_raw_iolist_int,3,[{file,\"src/couch_file.erl\"},{line,714}]},\n {couch_file,handle_call,3,[{file,\"src/couch_file.erl\"},{line,493}]},\n {gen_server,try_handle_call,4,[{file,\"gen_server.erl\"},{line,636}]},\n {gen_server,handle_msg,6,[{file,\"gen_server.erl\"},{line,665}]},\n {proc_lib,init_p_do_apply,3,[{file,\"proc_lib.erl\"},{line,247}]}]},\n {gen_server,call,[<0.784.0>,{pread_iolist,16830},infinity]},\n [{gen_server,call,3,[{file,\"gen_server.erl\"},{line,214}]},\n {couch_file,pread_iolist,2,[{file,\"src/couch_file.erl\"},{line,177}]},\n {couch_file,pread_binary,2,[{file,\"src/couch_file.erl\"},{line,172}]},\n {couch_file,pread_term,2,[{file,\"src/couch_file.erl\"},{line,160}]},\n {couch_btree,get_node,2,[{file,\"src/couch_btree.erl\"},{line,435}]},\n {couch_btree,reduce_stream_node,11,\n [{file,\"src/couch_btree.erl\"},{line,622}]},\n {couch_btree,fold_reduce,4,[{file,\"src/couch_bt
ree.erl\"},{line,81}]},\n {couch_bt_engine,count_changes_since,2,\n [{file,\"src/couch_bt_engine.erl\"},{line,646}]}]}"}
```
Response with the patch:
```erlang
{"error":"error","reason":"{{bad_return_value,\n {file_truncate_error,eof,\n \"/Users/jan/Work/asf/couchdb/dev/lib/node1/data/shards/00000000-ffffffff/x-test-goop.1618391080.couch\"}},\n {gen_server,call,[<0.6608.1>,{pread_iolist,16830},infinity]},\n [{gen_server,call,3,[{file,\"gen_server.erl\"},{line,214}]},\n {couch_file,pread_iolist,2,[{file,\"src/couch_file.erl\"},{line,177}]},\n {couch_file,pread_binary,2,[{file,\"src/couch_file.erl\"},{line,172}]},\n {couch_file,pread_term,2,[{file,\"src/couch_file.erl\"},{line,160}]},\n {couch_btree,get_node,2,[{file,\"src/couch_btree.erl\"},{line,435}]},\n {couch_btree,reduce_stream_node,11,\n [{file,\"src/couch_btree.erl\"},{line,622}]},\n {couch_btree,fold_reduce,4,[{file,\"src/couch_btree.erl\"},{line,81}]},\n {couch_bt_engine,count_changes_since,2,\n [{file,\"src/couch_bt_engine.erl\"},{line,646}]}]}"}
```
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[GitHub] [couchdb] bessbd commented on pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
bessbd commented on pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507#issuecomment-819456907
Should we open a follow-up issue / PR?
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[GitHub] [couchdb] janl merged pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
janl merged pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507
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[GitHub] [couchdb] rnewson commented on pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
rnewson commented on pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507#issuecomment-879229350
Yes, sorry for delay. +1.
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[GitHub] [couchdb] janl commented on pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
janl commented on pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507#issuecomment-877755965
@rnewson is this more in line with what you were looking for here?
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[GitHub] [couchdb] bessbd commented on pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
bessbd commented on pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507#issuecomment-819456737
The error message improvement seems awesome, but we still shouldn't get a stack trace on HTTP, right?
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[GitHub] [couchdb] rnewson commented on a change in pull request #3507: log file truncation
Posted by GitBox <gi...@apache.org>.
rnewson commented on a change in pull request #3507:
URL: https://github.com/apache/couchdb/pull/3507#discussion_r613406164
##########
File path: src/couch/src/couch_file.erl
##########
@@ -711,10 +711,21 @@ read_raw_iolist_int(Fd, {Pos, _Size}, Len) -> % 0110 UPGRADE CODE
read_raw_iolist_int(Fd, Pos, Len);
read_raw_iolist_int(#file{fd = Fd} = File, Pos, Len) ->
{Pos, TotalBytes} = get_pread_locnum(File, Pos, Len),
- {ok, <<RawBin:TotalBytes/binary>>} = file:pread(Fd, Pos, TotalBytes),
- {remove_block_prefixes(Pos rem ?SIZE_BLOCK, RawBin), Pos + TotalBytes}.
-
+ case catch file:pread(Fd, Pos, TotalBytes) of
+ {ok, <<RawBin:TotalBytes/binary>>} ->
+ {remove_block_prefixes(Pos rem ?SIZE_BLOCK, RawBin), Pos + TotalBytes};
+ Else ->
+ % This clause matches when the file we are working with got truncated
+ % outside of CouchDB after we opened it. To find affected files, we
+ % need to log the file path.
+ %
+ % Technically, this should also go into read_multi_raw_iolists_int/2,
+ % but that doesn’t seem to be in use anywhere.
+ {_Fd, Filepath} = get(couch_file_fd),
+ throw({file_truncate_error, Else, Filepath})
Review comment:
The original behaviour caused an `exit` which we're now softening to a `throw`. I think that's a mistake.
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